Ink jet printing method

ABSTRACT

An ink jet printing method, comprising the steps of: 
     A) providing an ink jet printer that is responsive to digital data signals; 
     B) loading the printer with an ink jet recording element comprising a support having thereon an image-receiving layer; 
     C) loading the printer with an ink jet ink composition comprising water, a humectant, a polyvalent transition metal complex of an 8-heterocyclylazo-5-hydroxy-quinoline and an anti-kogation material comprising an alkali metal salt of a monobasic organic or inorganic acid; and 
     D) printing on the image-receiving layer using the ink jet ink composition in response to the digital data signals. 
     Examples of anti-kogation materials useful in the invention include sodium hexanoate, sodium sulfate, sodium propionate, sodium benzoate, sodium p-toluenesulfonate, sodium acetate, sodium bromide, sodium nitrate, potassium nitrate, lithium nitrate, lithium acetate, tetramethylammonium acetate and tetrabutylammonium bromide.

CROSS REFERENCE TO RELATED APPLICATION

Reference is made to commonly assigned, co-pending U.S. patentapplication Ser. No. 09/794,608 by Erdtmann et al., (Docket 82240) filedof even date herewith entitled “Ink Jet Ink Composition”.

FIELD OF THE INVENTION

This invention relates to an ink jet printing method using a certainmetal complex useful as a colorant in combination with an anti-kogationmaterial in an ink jet ink composition.

BACKGROUND OF THE INVENTION

Ink jet printing is a non-impact method for producing images by thedeposition of ink droplets in a pixel-by-pixel manner to animage-recording element in response to digital signals. There arevarious methods which may be utilized to control the deposition of inkdroplets on the image-recording element to yield the desired image. Inone process, known as continuous ink jet, a continuous stream ofdroplets is charged and deflected in an imagewise manner onto thesurface of the image-recording element, while unimaged droplets arecaught and returned to an ink sump. In another process, known asdrop-on-demand inkjet, individual ink droplets are projected as neededonto the image-recording element to form the desired image. Commonmethods of controlling the projection of ink droplets in drop-on-demandprinting include piezoelectric transducers and thermal bubble formation.Ink jet printers have found broad applications across markets rangingfrom industrial labeling to short run printing to desktop document andpictorial imaging.

The inks used in the various ink jet printers can be classified aseither dye-based or pigment-based. A dye is a colorant, which isdissolved in the carrier medium. A pigment is a colorant that isinsoluble in the carrier medium, but is dispersed or suspended in theform of small particles, often stabilized against flocculation andsettling by the use of dispersing agents. The carrier medium can be aliquid or a solid at room temperature in both cases. Commonly usedcarrier media include water, mixtures of water and organic co-solventsand high boiling organic solvents, such as hydrocarbons, esters,ketones, etc.

The choice of a colorant in ink jet systems is critical to imagequality. For colors such as cyan, magenta, yellow, green, orange, etc.,the peak wavelength (λ-max), the width of the absorption curve and theabsence of secondary absorptions are important. The colorants shouldalso have a high degree of light fastness after printing onto theink-receiving element. For aqueous dye-based inks, the dyes need to besufficiently soluble in water to prepare a solution that is capable ofproducing adequate density on the receiving element and stable forextended periods of storage without precipitation. High quality ink jetprinting with dye-based inks requires dyes which will provide bothbright hue and good light stability. It is difficult to find dyes whichmeet all of these requirements, particularly magenta dyes.

Kogation occurs on a thermal ink jet heater plate as a result of thermaldecomposition of ink components or accumulation of intact inkcomponents. An anti-kogation material can be used in an ink jet inkcomposition to prevent buildup of thermal decomposition products on aheater plate in a thermal ink jet print head.

U.S. Pat. No. 6,001,161 relates to a magenta metal complex dye for anink jet ink. However, there is a problem with this dye in that themaximum density of a printed image decreases over time with magenta inkscontaining this dye.

U.S. Pat. No. 6,059,868 relates to anti-kogation materials useful in inkjet printing. However, when these anti-kogation materials are used withmetal-complex dyes, the resulting printed image have poor image quality.

It is an object of this invention to provide an ink jet printing methodusing an ink jet ink composition containing a magenta metal complex incombination with an anti-kogation material that has both good lightstability and bright hue, and is able to provide consistent density whenprinted in a thermal ink jet printer.

SUMMARY OF THE INVENTION

This and other objects are achieved in accordance with this inventionwhich relates to an inkjet printing method, comprising the steps of:

A) providing an ink jet printer that is responsive to digital datasignals;

B) loading the printer with an ink jet recording element comprising asupport having thereon an image-receiving layer,

C) loading the printer with an ink jet ink composition comprising water,a humectant, a polyvalent transition metal complex of an8-heterocyclylazo-5-hydroxy-quinoline and an anti-kogation materialcomprising an alkali metal salt of a monobasic organic or inorganicacid; and

D) printing on the image-receiving layer using the ink jet inkcomposition in response to the digital data signals.

Use of this ink composition in the inkjet printing method of theinvention provides images with a combination of outstanding lightstability, bright magenta hue and consistent densities.

DETAILED DESCRIPTION OF THE INVENTION

In a preferred embodiment of the invention, the polyvalent transitionmetal complexes of an 8-heterocyclylazo-5-hydroxyquinoline employed havethe following general structure:

wherein:

M represents a polyvalent transition metal ion;

each L independently represents a neutral or anionic ligand;

each X, Y and Z independently represents a substituted or unsubstitutedalkyl group of 1-6 carbon atoms, a substituted or unsubstituted alkylgroup of 6-10 carbon atoms, a substituted or unsubstituted hetaryl groupof 5-10 atoms, halogen, cyano, nitro, a substituted or unsubstitutedalkoxycarbonyl group of 1-6 carbon atoms, a substituted or unsubstitutedalkoxy group of 1-6 carbon atoms, hydroxy, a polyoxyalkylene group of2-20 alkylene oxide residues, carboxy or a salt thereof, sulfo or a saltthereof, phospho or a salt thereof, carbamoyl, a substituted orunsubstituted alkyl-, aralkyl-, aryl-, diaryl- or dialkyl-carbamoylgroup of 1-20 carbon atoms, sulfamoyl, a substituted or unsubstitutedalkyl-, aralkyl-, aryl-, diaryl- or dialkyl-sulfamoyl group of 1-20carbon atoms, acylamino, sulfonylamino, amino, a substituted orunsubstituted alkyl-, aralkyl-, aryl-, diaryl- or dialkyl-amino group of1-20 carbon atoms or a quaternary ammonium or phosphonium group;

Q represents the atoms necessary to complete a 5- or 6-memberedheterocyclic ring;

n represents 2 or 3;

m represents an integer from 1-3;

each p and r independently represents an integer from 0-3;

q represents 0, 1 or 2;

two or more of L may be joined together to form a bi- or tridentateligand which may optionally comprise another polydentate molecule of thesame or different structure as shown above;

one or more of L may be combined with X and/or Z;

one or more of X, Y and Z, together with the carbon to which they areattached, may independently represent a ring nitrogen; and

any two of X, Y or Z may be joined together to form a 5-7 memberedsaturated or unsaturated ring;

Compositions in which two or more of the above metal complex dyesrepresented by structure 1 are joined covalently are also considered tobe within the scope of this invention.

Preferred transition metal ions for 1 include Ni²⁺, Cu²⁺, Zn²⁺, Fe²⁺,Fe³⁺, Cr³⁺, Pd²⁺, Pt²⁺and Co²⁺.

Examples of neutral ligands (L) for 1 include water, pyridine,morpholine and ammonia. Examples of bi- and tri-dentate ligands includebipyridine, terpyridine, iminodiacetate, glycine and 8-hydroxyquinoline.

Examples of anionic ligands (L) include acetate, chloride and cyanate.

For X, Y and Z in 1, examples of a substituted or unsubstituted alkylgroup include methyl, ethyl, isopropyl, hydroxyethyl,3-(N,N-dimethylamino) propyl, sulfatoethyl and benzyl. Examples of asubstituted or unsubstituted aryl group include phenyl, naphthyl,4-chlorophenyl and 2-carboxyphenyl. Examples of a substituted orunsubstituted hetaryl group include pyridyl, imidazolyl and quinolyl.Examples of halogen include chloro, fluoro, bromo and iodo. Examples ofa substituted or unsubstituted alkoxy group include methoxy, isopropoxy,2-hydroxyethoxy and carboxymethoxy. Useful salts of carboxy, sulfo,phospho and sulfato include sodium, lithium, potassium,triethanolammonium, pyridinium and tetramethylammonium. Examples of asubstituted or unsubstituted alkyl-, aralkyl-, aryl-, diaryl- ordialkyl-carbamoyl group include N-methylcarbamoyl,N-methyl-N-(3-sulfophenyl)-carbamoyl, N-p-(trimethylammonium)phenylcarbamoyl and N,N-bis (4-carboxyphenyl) carbamoyl. Examples of asubstituted or unsubstituted alkyl-, aralkyl-, aryl-, diaryl- ordialkyl-sulfamoyl group include N-methylsulfamoyl,N-methyl-N-(3-sulfophenyl)-sulfamoyl,N-p-(trimethylammonium)phenylsulfamoyl and N,N-bis(4-carboxyphenyl)sulfamoyl. Examples of an acylamino group includeacetamido, carboxyethylacetamido and benzamido. Examples of a ureidogroup include n-methylureido, ureido and 3,5-bis carboxyphenylureido.Examples of a sulfonylamino group include methanesulfonamido,p-toluenesulfonamido and 2-(trimethlyammonium)ethanesulfonamido.Examples of a substituted or unsubstituted alkyl-, aralkyl-, aryl-,diaryl- or dialkyl-amino group include methylamino, N,N-dimethylamino,carboxymethylamino and 2,5-disulfoanilino. disulfoanilino. Examples of aquaternary ammonium group include trimethylammonium andbenzyldimethylammonium. Examples of a phosphonium group includetriphenylphosphonium and trimethylphosphonium.

Examples of heterocyclic ring systems completed by the atoms representedby Q include pyridine, pyrazine, quinoline, thiazole, benzothiazole andpyrazole.

In a preferred embodiment of the invention, M is Ni²⁺. In anotherpreferred embodiment, L_(m) comprises an8-heterocyclylazo-5-hydroxyquinoline. In yet another preferredembodiment, X is a chloro, methyl, alkoxy or carboxy. In still anotherpreferred embodiment, Y is hydrogen, and Z is hydrogen oralkylsulfamoyl. In still yet another preferred embodiment, Q representsthe atoms necessary to complete a pyridine ring.

U.S. Pat. No. 4,420,550 and Example 1 hereafter describe generalsynthetic procedures for preparing the metal complexes employed in thisinvention.

Representative examples of dyes which may be employed in this inventioninclude the following:

Dye M X₁ X₂ Z λ-max¹ 1 Ni Cl CO₂H SO₂NH(i-Pr) 559 2 Cu Cl CO₂HSO₂NH(i-Pr) 547 3 Ni Cl CO₂Na H 550 4 Ni Cl CO₂H H 551 5 Ni H CO₂H H 5466 Ni CH₃ CO₂H H 552 7 Ni CO₂H CO₂H H 554 ¹Measured in 1% aqueoustriethanolamine

Dye M^(n+) X Y Z  8 Ni²⁺ 3-CO₂H H H 4-Cl  9 Co²⁺ 2-Cl 6-CH₃ 5′-SO₃-Na⁺3-CH₃ 10 Cr³⁺ 2-Cl H 6′-Cl 3-CONH-(C₂H₄N(CH₃)₂) 11 Ni²⁺ H H4′,5′-(CO₂H)₂ 12 Cu²⁺ 2-NHC₃H₆N-(CH₃)₂ 6,7-(CH₃)₂ H 13 Ni²⁺ 2-Cl 7-CO₂H5′-Cl 3-[C₆H₃-3,5-(SO₃Na)₂] 14 Ni²⁺ 2,3-Cl₂ 6-OH 5′-SO₂NH[C₃H₆N(CH₃)₂]₂15 Cu²⁺ 3-CONHC₂H₄-(N⁺CH₃)₃Cl⁻ 6-CN 4′-CONH₂ 16 Ni²⁺ 2-Cl H H3-SO₂NHC₂H₄OSO₃-Na⁺

As noted above, an anti-kogation material is used in the ink jetcomposition of the invention and comprises an alkali metal salt of amonobasic organic or inorganic acid. In another preferred embodiment ofthe invention, the anti-kogation material is sodium hexanoate, sodiumsulfate, sodium propionate, sodium benzoate, sodium p-toluenesulfonate,sodium acetate, sodium bromide, sodium nitrate, potassium nitrate,lithium nitrate, lithium acetate, tetramethylammonium acetate ortetrabutylammonium bromide. The anti-kogation material may be present inthe ink jet ink composition in an amount of from about 0.1 to about 10weight %, preferably from about 0.25 to about 5 weight %.

A humectant is employed in the ink jet composition employed in theinvention to help prevent the ink from drying out or crusting in theorifices of the printhead. Examples of humectants which can be usedinclude polyhydric alcohols, such as ethylene glycol, diethylene glycol,triethylene glycol, propylene glycol, tetraethylene glycol, polyethyleneglycol, glycerol, 2-methyl-2,4-pentanediol 1,2,6-hexanetriol andthioglycol, lower alkyl mono- or di-ethers derived from alkyleneglycols, such as ethylene glycol mono-methyl or mono-ethyl ether,diethylene glycol mono-methyl or mono-ethyl ether, propylene glycolmono-methyl or mono-ethyl ether, triethylene glycol mono-methyl ormono-ethyl ether, diethylene glycol di-methyl or di-ethyl ether, anddiethylene glycol monobutylether; nitrogen-containing cyclic compounds,such as 2-pyrrolidone, N-methyl-2-pyrrolidone, and1,3-dimethyl-2-imidazolidinone; and sulfur-containing compounds such asdimethyl sulfoxide and tetramethylene sulfone. A preferred humectant forthe composition of the invention is diethylene glycol, glycerol,2-pyrrolidone or diethylene glycol monobutylether.

Water-miscible organic solvents may also be added to the aqueous inkemployed in the invention to help the ink penetrate the receivingsubstrate, especially when the substrate is a highly sized paper.Examples of such solvents include alcohols, such as methyl alcohol,ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol,sec-butyl alcohol, t-butyl alcohol, iso-butyl alcohol, furfuryl alcohol,and tetrahydrofurfuryl alcohol; ketones or ketoalcohols such as acetone,methyl ethyl ketone and diacetone alcohol; ethers, such astetrahydrofuran and dioxane; and esters, such as, ethyl lactate,ethylene carbonate and propylene carbonate.

Surfactants may be added to adjust the surface tension of the ink to anappropriate level. The surfactants may be anionic, cationic, amphotericor nonionic.

A biocide may be added to the composition employed in the invention tosuppress the growth of micro-organisms such as molds, fungi, etc. inaqueous inks. A preferred biocide for the ink composition employed inthe present invention is Proxel® GXL (Zeneca Specialties Co.) at a finalconcentration of 0.05-0.5 wt. %.

The pH of the aqueous ink compositions employed in the invention may beadjusted by the addition of organic or inorganic acids or bases. Usefulinks may have a preferred pH of from about 2 to 10, depending upon thetype of dye or pigment being used. Typical inorganic acids includehydrochloric, phosphoric and sulfuric acids. Typical organic acidsinclude methanesulfonic, acetic and lactic acids. Typical inorganicbases include alkali metal hydroxides and carbonates. Typical organicbases include ammonia, triethanolamine and tetramethylethlenediamine.

A typical ink composition of the invention may comprise, for example,the following substituents by weight: colorant (0.05-5%), water(20-95%), humectant (5-70%), water miscible co-solvents (2-20%),surfactant (0.1-10%), biocide (0.05-5%) and pH control agents (0.1-10%).

Additional additives which may optionally be present in the ink jet inkcomposition employed in the invention include thickeners, conductivityenhancing agents, drying agents, and defoamers.

The ink jet inks employed in this invention may be employed in ink jetprinting wherein liquid ink drops are applied in a controlled fashion toan ink receptive layer substrate, by ejecting ink droplets from aplurality of nozzles or orifices of the print head of an inkjet printer.

Ink-receptive substrates useful in inkjet printing are well known tothose skilled in the art. Representative examples of such substrates aredisclosed in U.S. Pat. Nos. 5,605,750; 5,723,211; and 5,789,070 and EP813 978 A1, the disclosures of which are hereby incorporated byreference.

The following examples illustrate the utility of the present invention.

EXAMPLES Example 1 Synthesis of Dye 6

A solution of 2.75 g (0.01 mole)ethyl-(2-methyl-5,8-dimethoxy)-quinoline-3-carboxylate (see U.S. Pat.No. 4,656,283) in 50 mL of tetrahydrofuran (THF) was diluted with 100 mLof ethylacetate. To this solution was added a solution of 13.71 g (0.025mole) of ceric ammonium nitrate in 50 mL of water and the 2-phasemixture stirred at room temperature for 1.5 hr. The phases wereseparated and the upper, organic layer washed twice with 25 mL of waterand once with saturated NaCl. After drying over MgSO₄, the organic layerwas evaporated to dryness at less than 40° C. The residual solid wassuspended in 100 mL of ethanol containing 0.5 mL of concentratedhydrochloric acid and treated with a solution of 1.09 g (0.01 mole) of2-hydrazinopyridine in 20 mL of ethanol containing 0.5 mL ofconcentrated hydrochloric acid. After stirring 18 hr at ambienttemperature and chilling to 0° C., the solid product was collected byfiltration. The crude dye-ester was purified by digestion with 25 mL ofboiling ethanol, chilling and filtering. The yield was 1.3 g (51% oftheory) ofethyl-(2-methyl-5-hydroxy-8-[2-pyridylazo])-quinoline-3-carboxylate as adark red solid.

The dye-ester from above (1.18 g, 0.0035 mole) was hydrolyzed by warmingat 40° C. in a mixture of THF/methanol/water (7:25:5) containing 0.7 gNaOH (0.0175 mole) for 2 hr. After dilution with 100 mL water, the deeporange solution was acidified to pH ˜3 with dilute hydrochloric acid andthe resulting yellow-orange solid collected by filtration. The crudedye-acid was purified by digestion with 15 mL of boiling acetonitrile,chilling and filtering to give 1.0 g (92% of theory) of2-methyl-5-hydroxy-8-(2-pyridylazo)-quinoline-3-carboxylic acid.

The dye-acid from above (1.0 g, 0.00325 mole) was suspended in 10 mL ofdimethylformamide and treated with a solution of 0.4 g (0.00162 mole)nickel(II)acetate tetrahydrate in 3 mL water. The red-magenta solutionwas warmed at 75° C. for 1 hour, cooled to ambient temperature anddiluted with 50 mL water and the crude Dye 6 was collected byfiltration. After digestion with 20 mL of acetonitrile, chilling andfiltering, 1.0 g (91% of theory) of Dye 6 was obtained as a darkred-green solid. The UV-visible spectrum was obtained in 1%triethanolamine/water and gave a λ-max of 552 nm. The mass spectrum wasdetermined with a quadropole mass spectrometer utilizing ElectrosprayIonization set up to detect negatively charged ions. The spectrumexhibited major peaks at m/e 671 and 673 consistent with the structureof Dye 6 (formula weight 672, ⁵⁸Ni),

Preparation of inks

Control Ink C-1:

One liter of ink was prepared containing 0.55% dry Dye 6, 7.5%diethylene glycol, 7.5% glycerol, 4.0% 2-pyrrolidinone, 0.30% Surfynol®465 (Air Products), 0.10% of Rhodia Rhodasurf® LA-9, and the balancedeionized water. The ink pH was adjusted to approximately 7 by theaddition of triethanolamine. The ink loaded into a 25.4 cm AlleghenyBradford filter housing and filtered through a Pall® 4.5 μ filterfollowed by a Pall® DFA filter.

Control Ink C-2:

One liter of ink was prepared like Control Ink C-1, except 0.90%ammonium nitrate (Acros) was added. Ammonium nitrate is an anti-kogationmaterial described in U.S. Pat. No. 6,059,868 (see Liquids 1b, 1c, 2b,2c, 3b and 3c in Table VI).

Control Ink C-3:

One liter of ink was prepared like Control Ink C-1, except 0.60% sodiumcarbonate (Aldrich), an alkali metal salt of a dibasic inorganic acid,was added.

Control Ink C-4:

One liter of ink was prepared like Control Ink C-1, except 1.26% sodiumtartrate dihydrate (Kodak), an alkali metal salt of a dibasic organicacid, was added.

Control Ink C-5:

One liter of ink was prepared like Control Ink C-1, except 1.08% sodiumcitrate dihydrate (Kodak), an alkali metal salt of a dibasic organicacid, was added.

Invention Ink 1:

One liter of ink was prepared like Control Ink C-1, except 0.90% sodiumhexanoate (Aldrich) was added.

Invention Ink 2:

One liter of ink was prepared like Control Ink C-1, except 1.56% sodiumsulfate (Aldrich) was added.

Invention Ink 3:

One liter of ink was prepared like Control Ink C-1, except 1.07% sodiumpropionate (Aldrich) was added.

Invention Ink 4:

One liter of ink was prepared like Control Ink C-1, except 1.60% sodiumbenzoate (Kodak) was added.

Invention Ink 5:

One liter of ink was prepared like Control Ink C-1, except 2.16% sodiump-toluene sulfonate, sodium salt (Aldrich) was added.

Invention Ink 6:

One liter of ink was prepared like Control Ink C-1, except 1.13%potassium nitrate (Aldrich) was added.

Invention Ink 7:

One liter of ink was prepared like Control Ink C-1, except 0.76% lithiumnitrate (Aldrich) was added.

Invention Ink 8:

One liter of ink was prepared like Control Ink C-1, except 0.90% sodiumnitrate (Kodak) was added.

Invention Ink 9:

One liter of ink was prepared like Control Ink C-1, except 0.90% sodiumacetate (Aldrich) was added.

Invention Ink 10:

One liter of ink was prepared like Control Ink C-1, except 3.53%tetrabutylammonium bromide (Aldrich) was added.

Invention Ink 11:

One liter of ink was prepared like Control Ink C-1, except 1.11% sodiumbromide (EM Science) was added.

Printing of test images

Each of the above inks was filled into a reservoir of an Encad 700printer and into an empty Encad GS ink cartridge. An image qualitytarget that contained a small 2.0 square cm magenta patch was printedonto KODAK PROFESSIONAL EI Premium Media and the initial density wasmeasured using an X-Rite densitometer. A prime target was printed tomake sure all of the nozzles were firing correctly and there were noelectrical failures. An electrical failure may occur when there iseither an electrical short to ground so that the heater is by-passed andinsufficient heat is generated in the heater, or there is a significantincrease in resistance in the heater circuit, which would also inhibitgeneration in the heater in the printhead. Either of these phenomenacauses the nozzle not to operate.

A large 100% magenta patch target (92 by 610 cm) was then printed thatconsumed 25 ml of ink. A second image quality target was printed ontoKODAK PROFESSIONAL El Premium Media and the density was re-measured. Aprime target was printed to make sure all of the nozzles were firingcorrectly and there were no electrical failures. This test was repeateduntil a total of 300 ml of ink was fired through a single Encadprinthead. The percent density retained between the initial imagequality target and the image quality target printed after 300 ml of inkhad been fired is shown in Table 1. If any nozzles have had anelectrical failure during the 300 ml test, it is recorded in Table 1,and the ink is considered unacceptable.

Each image quality target was evaluated for image defects such asbanding, bronzing, or bleed. A qualitative rating of excellent, good,fair, and poor was given to each ink printed onto KODAK PROFESSIONAL EIPremium Media, and is shown in Table 1. An ink must have improveddensity retention, excellent or good image quality, and no electricalfailures to be considered acceptable.

TABLE 1 Percent Density Ink Retained Image Quality Electrical Failure 183% Excellent No 2 83% Excellent No 3 89% Excellent No 4 89% ExcellentNo 5 85% Excellent No 6 100%  Excellent No 7 95% Excellent No 8 89%Excellent No 9 88% Excellent No 10  93% Good No 11  86% Excellent No C-166% Excellent No C-2 100%  Poor No C-3 100%  Excellent Yes C-4 79%Excellent Yes C-5 84% Excellent Yes

The above results show that the inkjet ink compositions employed in theinvention yield images with excellent image quality, have improvedretained density, and do not cause electrical failures of the printhead.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

What is claimed is:
 1. An ink jet printing method, comprising the stepsof: A) providing an ink jet printer that is responsive to digital datasignals; B) loading said printer with an ink jet recording elementcomprising a support having thereon an image-receiving layer; C) loadingsaid printer with an ink jet ink composition comprising water, ahumectant, a polyvalent transition metal complex of an8-heterocyclylazo-5-hydroxy-quinoline and a separate anti-kogationmaterial comprising an alkali metal salt of a monobasic organic orinorganic acid; and D) printing on said image-receiving layer using saidink jet ink composition in response to said digital data signals.
 2. Themethod of claim 1 wherein said complex has the following structure:

wherein: M represents a polyvalent transition metal ion; each Lindependently represents a neutral or anionic ligand; each X, Y and Zindependently represents a substituted or unsubstituted alkyl group of1-6 carbon atoms, a substituted or unsubstituted aryl group of 6-10carbon atoms, a substituted or unsubstituted hetaryl group of 5-10atoms, halogen, cyano, nitro, a substituted or unsubstitutedalkoxycarbonyl group of 1-6 carbon atoms, a substituted or unsubstitutedalkoxy group of 1-6 carbon atoms, hydroxy, a polyoxyalkylene group of2-20 alkylene oxide residues, carboxy or a salt thereof, sulfo or a saltthereof, phospho or a salt thereof, carbamoyl, a substituted orunsubstituted alkyl-, aralkyl-, aryl-, diaryl- or dialkyl-carbamoylgroup of 1-20 carbon atoms, sulfamoyl, a substituted or unsubstitutedalkyl-, aralkyl-, aryl-, diaryl- or dialkyl-sulfamoyl group of 1-20carbon atoms, acylamino, sulfonylamino, amino, a substituted orunsubstituted alkyl-, aralkyl-, aryl-, diaryl- or dialkyl-amino group of1-20 carbon atoms or a quaternary ammonium or phosphonium group; Qrepresents the atoms necessary to complete a 5- or 6-memberedheterocyclic ring; n represents 2 or 3; m represents an integer from1-3; each p and r independently represents an integer from 0-3; qrepresents 0, 1 or 2; two or more of L may be joined together to form abi- or tridentate ligand which may optionally comprise anotherpolydentate molecule of the same or different structure as shown above;one or more of L may be combined with X and/or Z; one or more of X, Yand Z, together with the carbon to which they are attached, mayindependently represent a ring nitrogen; and any two of X, Y or Z may bejoined together to form a 5-7 membered saturated or unsaturated ring. 3.The method of claim 2 wherein M is Ni²⁺.
 4. The method of claim 2wherein L_(m) comprises an 8-heterocyclylazo-5-hydroxyquinoline.
 5. Themethod of claim 2 wherein X is chloro, methyl, alkoxy or carboxy.
 6. Themethod of claim 2 wherein Y is hydrogen.
 7. The method of claim 2wherein Z is hydrogen or alkylsulfamoyl.
 8. The method of claim 2wherein Q represents the atoms necessary to complete a pyridine ring. 9.The method of claim 1 wherein said composition also contains awater-miscible organic solvent.
 10. The method of claim 1 wherein saidhumectant is diethylene glycol, glycerol, 2-pyrrolidinone or diethyleneglycol monobutylether.
 11. The method of claim 1 wherein said metalcomplex comprises about 0.05 to about 5% by weight of said ink jet inkcomposition.
 12. The method of claim 1 wherein said anti-kogationmaterial is present in said ink jet ink composition in an amount of fromabout 0.1 to about 10 weight %.
 13. The method of claim 1 wherein saidanti-kogation material is present in said ink jet ink composition in anamount of from about 0.25 to about 5 weight %.
 14. An ink jet printingmethod, comprising the steps of: A) providing an ink jet printer that isresponsive to digital data signals; B) loading said printer with an inkjet recording element comprising a support having thereon animage-receiving layer; C) loading said printer with an ink jet inkcomposition comprising water, a humectant, a polyvalent transition metalcomplex of an 8-heterocyclylazo-5-hydroxy-quinoline and a separateanti-kogation material comprising sodium hexanoate, sodium sulfate,sodium propionate, sodium benzoate, sodium p-toluenesulfonate, sodiumacetate, sodium bromide, sodium nitrate, potassium nitrate, lithiumnitrate, lithium acetate, tetramethylammonium acetate ortetrabutylammonium bromide; and D) printing on said image-receivinglayer using said ink jet ink composition in response to said digitaldata signals.
 15. The method of claim 14 wherein said complex has thefollowing structure:

wherein: M represents a polyvalent transition metal ion; each Lindependently represents a neutral or anionic ligand; each X, Y and Zindependently represents a substituted or unsubstituted alkyl group of1-6 carbon atoms, a substituted or unsubstituted aryl group of 6-10carbon atoms, a substituted or unsubstituted hetaryl group of 5-10atoms, halogen, cyano, nitro, a substituted or unsubstitutedalkoxycarbonyl group of 1-6 carbon atoms, a substituted or unsubstitutedalkoxy group of 1-6 carbon atoms, hydroxy, a polyoxyalkylene group of2-20 alkylene oxide residues, carboxy or a salt thereof, sulfo or a saltthereof, phospho or a salt thereof, carbamoyl, a substituted orunsubstituted alkyl-, aralkyl-, aryl-, diaryl- or dialkyl-carbamoylgroup of 1-20 carbon atoms, sulfamoyl, a substituted or unsubstitutedalkyl-, aralkyl-, aryl-, diaryl- or dialkyl-sulfamoyl group of 1-20carbon atoms, acylamino, sulfonylamino, amino, a substituted orunsubstituted alkyl-, aralkyl-, aryl-, diaryl- or dialkyl-amino group of1-20 carbon atoms or a quaternary ammonium or phosphonium group; Qrepresents the atoms necessary to complete a 5- or 6-memberedheterocyclic ring; n represents 2 or 3; m represents an integer from1-3; each p and r independently represents an integer from 0-3; qrepresents 0, 1 or 2; two or more of L may be joined together to form abi- or tridentate ligand which may optionally comprise anotherpolydentate molecule of the same or different structure as shown above;one or more of L may be combined with X and/or Z; one or more of X, Yand Z, together with the carbon to which they are attached, mayindependently represent a ring nitrogen; and any two of X, Y or Z may bejoined together to form a 5-7 membered saturated or unsaturated ring.16. The method of claim 14 wherein said metal complex comprises about0.05 to about 5% by weight of said ink jet ink composition.
 17. Themethod of claim 14 wherein said anti-kogation material is present insaid ink jet ink composition in an amount of from about 0.1 to about 10weight %.
 18. The method of claim 14 wherein said anti-kogation materialis present in said ink jet ink composition in an amount of from about0.25 to about 5 weight %.